1. Technical Field
This invention relates generally to a vehicle cooling system, and particularly to a control apparatus for controlling cooling of a vehicle radiator and air-conditioning condenser.
2. Discussion
A vehicle cooling apparatus is disclosed in Japanese Patent Application Laid-Open No. Hei. 4-365923. In this related art apparatus, an electric cooling fan for drawing cooling air through a radiator is controlled by pulse width modulation (PWM) in correspondence with the temperature of cooling water passing through the radiator.
In such an apparatus, a main battery and a sub battery are mounted in the vehicle, and the sub battery is used when the cooling water temperature reaches a predetermined high temperature. More particularly, the main battery and the sub battery are connected in series, and, when the cooling water temperature reaches the predetermined high temperature, the input power of a cooling fan electric motor is increased above the motor's rated input power (motor rated input power is defined as the input power of a motor in a control circuit in which an air conditioner start-up fan control voltage, or a fan voltage reached when refrigerant pressure exceeds a predetermined value, approximately equals a vehicle battery voltage under a vehicle standard voltage).
However, because the above apparatus requires two batteries, space required for the apparatus and overall vehicle cost are both increased. Also, because a switching circuit for the main battery/sub battery series connection is required, the number of parts and overall system complexity are increased.